These projects are designed to further our knowledge of chromatin replication. Histone deposition is a major aspect of this replication, as these proteins are required to package DNA such that it is accessible to effector molecules and polymerases. We specifically plan to study the organization of nucleosomes with respect to the two daughter strands to determine whether the deposition of histones during replication provides a mechanism for passing epigenetic information from parent to daughter cells. We plan to study the histone exchange process (histone H2A, H2B and the histone variants) to determine whether this process reflects nucleosome instability due to ongoing gene activity. We plan to study the relationship between histone deposition and the maturation of Okazaki fragments, a relationship that may have been misinterpreted previously as conservative deposition of histones in SV40 infected cells. We plan to study the stability of the prereplicational nucleosome to determine whether its dissolution is required for DNA replication. We plan to study the assembly process in nucleosome formation by analyzing the histone:histone interactions that are occurring in vivo during nucleosome formation. We plan to isolate depositional factors from G1 and hydroxyurea-treated cells to assay in vitro why there is a difference in the ability of these two systems to deposit histones. These studies will be done in SV40- infected cells and in transformed cells which differ in replication characteristics. These experiments will provide us with a better understanding of chromatin replication and perhaps clinically a means for destroying cell systems where this process is uncontrolled.